Semi tractor trailers are loaded and coupled to semi tractors. The semi tractor truck can then be used to move the trailer and the content of the trailer to any desired location. Semi tractors and trailers are used widely in moving commercial goods. Semi tractors and trailers can also be used to move livestock to markets or move a family's personal belongings to a new house hundreds or even thousands of miles away.
Operators of semi trucks, in many instances, disconnect a semi trailer. For example, the operators of semi trucks generally make money while hauling loaded trailers from one spot to another. Therefore, the operator may disconnect a loaded semi trailer when it has reached a destination. The trailer can then be unloaded while the operator of the semi moves another loaded trailer elsewhere. In another instance, the operator may disconnect an empty semi trailer at a location. The trailer can be loaded while the semi tractor is used for other jobs. The operator can then come back and reconnect the now loaded semi trailer and haul it to a selected destination.
Many semi trailers are without a front axle and without front wheels. Generally, the weight of the semi trailer is borne by a fifth wheel on a semi tractor when the semi trailer is attached to the semi tractor. When disconnected, legs known as dollies are used to hold up the end of the semi trailer without the front axle or front wheels. When a full trailer is supported by the legs, a large force is carried on the legs. The semi tractor is generally backed into position where the semi trailer can be attached to the fifth wheel. The chore that remains includes retracting the legs to place the full weight of the semi trailer onto the fifth wheel portion of the semi tractor. A set of gears are turned to retract the legs. When the semi-trailer is loaded, the gears are very difficult to turn. Semi tractor operators can get hurt exerting the amount of force needed to turn the gears to retract the legs. If the semi tractor operator is an employee of a company, workman's compensation claims can result. This can be costly to the owner of a fleet of semi tractors. In addition to potential injuries to semi tractor operators, the large forces needed to turn the gears associated with the dollies can strip the gears. This is again costly in that the parts are expensive and must be replaced before moving the semi trailer. This wastes an operators time in addition to incurring the repair cost. Customers may also be disappointed as the arrival of their freight or cargo in the semi trailer may be delayed. Again, this can result in additional monetary losses if a contract covering the transaction includes penalty costs for delaying shipment. Even if the gears are not stripped, turning the gears under a heavy load wears the gears so that their life is shortened. In other words, the time between stripping the gears associated with the dollies may be shorter than necessary.